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com.tangosol.util.aggregator
Class TopNAggregator

java.lang.Object
com.tangosol.util.aggregator.TopNAggregator

All Implemented Interfaces:

ExternalizableLite, PortableObject, InvocableMap.EntryAggregator, InvocableMap.ParallelAwareAggregator, InvocableMap.ParallelAwareAggregator.PartialResultAggregator, java.io.Serializable

public class TopNAggregator

extends java.lang.Object

implements InvocableMap.ParallelAwareAggregator, InvocableMap.ParallelAwareAggregator.PartialResultAggregator, ExternalizableLite, PortableObject

TopNAggregator is a ParallelAwareAggregator that aggregates the top N extracted values into an array. The extracted values must not be null, but do not need to be unique.

Author:

rhl 2013.04.24

Nested Class Summary

static class

TopNAggregator.PartialResult The sorted partial result.

Nested classes/interfaces inherited from interface com.tangosol.util.InvocableMap.ParallelAwareAggregator

InvocableMap.ParallelAwareAggregator.PartialResultAggregator

Field Summary

protected java.util.Comparator	m_comparator The Comparator used to order the extracted values.
protected int	m_cResults The maximum number of results to include in the aggregation result.
protected ValueExtractor	m_extractor The ValueExtractor used by this aggregator.
protected boolean	m_fParallel True iff this aggregator is to be used in parallel.

Constructor Summary

TopNAggregator()
Default constructor.

TopNAggregator(ValueExtractor extractor, java.util.Comparator comparator, int cResults)
Construct a TopNAggregator that will aggregate the top extracted values, as determined by the specified comparator.

Method Summary

protected void	addToResult(java.util.Iterator iterValues, TopNAggregator.PartialResult result) Add the specified values to the result if they are within the top-N.
java.lang.Object	aggregate(java.util.Set setEntries) Process a set of InvocableMap.Entry objects in order to produce an aggregated result.
java.lang.Object	aggregatePartialResults(java.util.Collection colPartialResults) Aggregate the results of the parallel aggregations, producing a partial result logically representing the partial aggregation.
java.lang.Object	aggregateResults(java.util.Collection colResults) Aggregate the partial results of the parallel aggregations into a final result.
protected java.lang.Object[]	finalizeResult(TopNAggregator.PartialResult result) Finalize the partial aggregation result.
InvocableMap.EntryAggregator	getParallelAggregator() Get an aggregator that can take the place of this aggregator in situations in which the InvocableMap can aggregate in parallel.
void	readExternal(java.io.DataInput in) Restore the contents of this object by loading the object's state from the passed DataInput object.
void	readExternal(PofReader in) Restore the contents of a user type instance by reading its state using the specified PofReader object.
void	writeExternal(java.io.DataOutput out) Save the contents of this object by storing the object's state into the passed DataOutput object.
void	writeExternal(PofWriter out) Save the contents of a POF user type instance by writing its state using the specified PofWriter object.

Field Detail

m_fParallel

protected boolean m_fParallel

True iff this aggregator is to be used in parallel.

m_extractor

protected ValueExtractor m_extractor

The ValueExtractor used by this aggregator.

m_comparator

protected java.util.Comparator m_comparator

The Comparator used to order the extracted values.

m_cResults

protected int m_cResults

The maximum number of results to include in the aggregation result.

Constructor Detail

TopNAggregator

public TopNAggregator()

Default constructor.

TopNAggregator

public TopNAggregator(ValueExtractor extractor,
                      java.util.Comparator comparator,
                      int cResults)

Construct a TopNAggregator that will aggregate the top extracted values, as determined by the specified comparator.

Parameters:

extractor - the extractor

comparator - the comparator for extracted values

cResults - the maximum number of results to return

Method Detail

getParallelAggregator

public InvocableMap.EntryAggregator getParallelAggregator()

Get an aggregator that can take the place of this aggregator in situations in which the InvocableMap can aggregate in parallel.

If the returned aggregator is a InvocableMap.ParallelAwareAggregator.PartialResultAggregator, the partial results of the parallel aggregation may be further aggregated where optimal.

Specified by:

getParallelAggregator in interface InvocableMap.ParallelAwareAggregator

Returns:

the aggregator that will be run in parallel

aggregateResults

public java.lang.Object aggregateResults(java.util.Collection colResults)

Aggregate the partial results of the parallel aggregations into a final result.

Specified by:

aggregateResults in interface InvocableMap.ParallelAwareAggregator

Parameters:

colResults - the parallel aggregation results

Returns:

the aggregation of the parallel aggregation results

aggregate

public java.lang.Object aggregate(java.util.Set setEntries)

Process a set of InvocableMap.Entry objects in order to produce an aggregated result.

Specified by:

aggregate in interface InvocableMap.EntryAggregator

Parameters:

setEntries - a Set of read-only InvocableMap.Entry objects to aggregate

Returns:

the aggregated result from processing the entries

aggregatePartialResults

public java.lang.Object aggregatePartialResults(java.util.Collection colPartialResults)

Aggregate the results of the parallel aggregations, producing a partial result logically representing the partial aggregation. The returned partial result will be further aggregated to produce the final result.

Specified by:

aggregatePartialResults in interface InvocableMap.ParallelAwareAggregator.PartialResultAggregator

Parameters:

colPartialResults - the partial results

Returns:

an aggregation of the collection of partial results

addToResult

protected void addToResult(java.util.Iterator iterValues,
                           TopNAggregator.PartialResult result)

Add the specified values to the result if they are within the top-N.

Parameters:

iterValues - the iterator of values to add

result - the result

finalizeResult

protected java.lang.Object[] finalizeResult(TopNAggregator.PartialResult result)

Finalize the partial aggregation result.

Parameters:

result - the partial result

Returns:

the final aggregation result

readExternal

public void readExternal(java.io.DataInput in)
                  throws java.io.IOException

Restore the contents of this object by loading the object's state from the passed DataInput object.

Specified by:

readExternal in interface ExternalizableLite

Parameters:

in - the DataInput stream to read data from in order to restore the state of this object

Throws:

java.io.IOException - if an I/O exception occurs

java.io.NotActiveException - if the object is not in its initial state, and therefore cannot be deserialized into

writeExternal

public void writeExternal(java.io.DataOutput out)
                   throws java.io.IOException

Save the contents of this object by storing the object's state into the passed DataOutput object.

Specified by:

writeExternal in interface ExternalizableLite

Parameters:

out - the DataOutput stream to write the state of this object to

Throws:

java.io.IOException - if an I/O exception occurs

readExternal

public void readExternal(PofReader in)
                  throws java.io.IOException

Restore the contents of a user type instance by reading its state using the specified PofReader object.

Specified by:

readExternal in interface PortableObject

Parameters:

in - the PofReader from which to read the object's state

Throws:

java.io.IOException - if an I/O error occurs

writeExternal

public void writeExternal(PofWriter out)
                   throws java.io.IOException

Save the contents of a POF user type instance by writing its state using the specified PofWriter object.

Specified by:

writeExternal in interface PortableObject

Parameters:

out - the PofWriter to which to write the object's state

Throws:

java.io.IOException - if an I/O error occurs

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